Hey, we already know that life is unfair, and that baseball is unfair, and that when you try to mix the two together you can wind up with some unbelievably unjust circumstances.

If baseball (or life) was fair, Pedro Martinez would be pitching Game 1 for the Mets against the Dodgers tomorrow afternoon, and Duaner Sanchez would be pitching the eighth inning, and Xavier Nady would be playing right field and batting seventh. If life (or baseball) was fair, Yankees fans who’d used StubHub this year wouldn’t currently be blacklisted like McCarthy-era screenwriters.

But it isn’t. That’s the truth.

That’s reality. And so when the starting lineups are presented at Shea tomorrow, right around a quarter to four or so, Cliff Floyd should be introduced early, along with the rest of the Mets’ reserve players, coaches, trainers, and pitchers. And Endy Chavez should be announced as part of the starting lineup, batting eighth, playing left field.

Of all the Mets who will take part in the franchise’s first postseason innings in six years, none will relish the moment more than Floyd, and none will have earned those moments more. It wasn’t long ago that Floyd was one of the only reasons to come to Shea Stadium, to see him take aim at the back fence of the rightfield bullpen, because lord knows the baseball itself wasn’t a satisfying enough experience at Shea.

But sentimentality in October is a wonderful way to get yourself beat. Floyd is hurting. It’s painful to watch him run down fly balls, despite the fact that his heart is in every step, a heart as big as Flushing Bay. It’s painful to watch him run the bases. It’s painful to realize that, in what should be the culmination of four fine years as a Met, Floyd is less than 100 percent, maybe less than 70 percent.

But Willie Randolph has lived through more Octobers than just about anyone, and he’s seen what happens when managers make difficult decisions. He saw Billy Martin bench Reggie Jackson one decisive Game 5 night in Kansas City. He saw Joe Torre bench Wade Boggs and Tino Martinez in the 1996 World Series. Surely by now he knows that Bernie Williams, one of the great October Yankees of all time, will be reduced to pinchhitting duties this October, unless something unforeseen happens.

Johnny Keane, managing the Cardinals against the Yankees 42 Octobers ago, was asked why he’d stuck with Bob Gibson in a game long after the great pitcher had started leaking oil, and Keane famously replied, “I had a commitment to his heart.” It’s a wonderful sentiment. Surely, it’s one Randolph might echo if he decides to tab Floyd to start tomorrow afternoon.

In this case, that would be a mistake.

Offense shouldn’t be a concern for the Mets to begin with, although even in that area Chavez’ .779 OPS is 48 points higher than Floyd’s (as is his batting average against lefties – .333 to .179 – and Hong-Chih Kuo will start Game 2 for L.A.). Against the Dodgers, Chavez’ value will be on the basepaths, as another nuisance for L.A. to deal with, and in the outfield, chasing balls into the gaps and down the line that Floyd wouldn’t track down with a golf cart.

It will be difficult for Randolph to make that call, sure. Floyd is a popular figure in that clubhouse, and with good reason. And Randolph is nothing if not unfailingly loyal. Floyd has certainly earned his place of prominence on the Mets’ roster, and if he’s the lineup no one will complain too loudly.

Not until he plays on a hop a ball Chavez might have caught.

Not until he stops at second on a Jose Reyes single to left-center in the bottom of the sixth, where Chavez would have made it to third standing up. If the Mets get to the World Series, their problems will be solved half the time, thanks to the DH. But in order to get to that World Series, the Mets’ would-be DH has to step aside.

Maybe if life (and National League baseball) was fair, there would be a DH. But it isn’t, and so there isn’t. And so Cliff Floyd must serve a different role: cheerleader and hellacious late-inning pinch hitting option. It’s the Mets’ best option. And may be, in truth, their only one.